1. Field
The present invention discloses a method and system for lane relative position estimation for driver assistance systems or autonomous driving. Driver assistance systems may be part of a car, bike, scooter or any other road vehicle.
The invention is in the field of driver assistance based on computer vision or other sensing techniques perceiving the surrounding of a vehicle, in particular a road vehicle, and processing the sensory input to generate system relevant information.
The invention can in particular be implemented in a sensor-based computing module, which can be part of a car, a motorbike, or any other land-based vehicle. The invention can be applied in realistic real-world traffic environments, such as e.g. encountered when driving a car on inner-city roads.
2. Description of the Related Art
In modern vehicles a human driver is often assisted by “active safety systems”. Such active safety systems (in the following also referred to as “driver assistance systems”), which can e.g. be a lane keeping assistance system as described in U.S. Pat. No. 6,212,453 B1, physically sense the environment of the vehicle and extract information which then can be used for performing a driver assistance function. Based on this sensor signal processing the driver assistance system outputs a signal which can be fed to visual and/acoustic representations means, or it can be fed to an actuator the action of which alters the state of the vehicle. Such actuation can for example influence steering, decelerating or accelerating of a vehicle. Furthermore, pre-tensioning of a safety belt or deployment of an airbag system may be based on information contained in such signal.
State-of-the-art lane keeping assistance systems focus on the detection of the lane delimiting elements. For this, they typically detect the position of lane markings as described in US 20070198146 A1, JP 2007004669 A, or US 2011044503 A1. Alternatively curbstones can be detected which is described in US 20110063097 A1. But the determination of a lane area on the basis of lane delimiting elements can of course be based on other lane delimiting elements such as barriers as known from US 2011187863 A1. The determination is performed by processing signals obtained from a sensor.
A vehicle which comprises such a system and for which a traffic situation shall be analyzed or evaluated is called ego-vehicle and the lane on which such ego-vehicle currently is located is called ego-lane. These systems use the positions or course of detected delimiting elements for extracting a parameterized description of the ego-lane, e.g. curvature, width, or length of the ego-lane ahead. To this end, a particular lane model as described in U.S. Pat. No. 7,151,996 B2 can be used for extracting and tracking of model parameters based on the detected course of delimiter positions. Based on the lane model parameters, the lateral positioning of the current (or future) ego-vehicle locations within the lane can then be obtained.
Instead of detecting the delimiting elements directly, also a part-based representation has been used for lane/road detection which is disclosed in “Efficient Scene Understanding for Intelligent Vehicles Using a Part-Based Road Representation”, D. Toepfer, J. Spehr, J. Effertz, C. Stiller, Intelligent Transportation Systems Conference 2013. A part is defined as a 2D lane area having a width and height and delimiters on right and left side each. Instead of an explicit binary detection, a probability value for edge/lane marking detection is allowed. By applying variations of the 2D basic area (position, orientation, width, height) one obtains a probability distribution of lane parts in an image. These lane parts have been fused in a hierarchical representation to detect 1) the overall lane shape as concatenation of lane parts and 2) the overall road consisting of several lanes. Again, this road model then allows calculating the lateral positioning of other vehicles and the ego-vehicle.
Lateral positioning is highly relevant for lane keeping assistance systems and is termed the lane relative position in the context of the present invention. In general, the lane relative position can be defined as continuous value that represents the lateral positioning of a particular location of a road within its lane, i.e., relative to its lane boundaries.
For example, identifying the lane relative position of a location on the road can be used as indication how well the ego-vehicle is currently laterally centered within its lane which is described in WO 2012/126650 A1 or whether it is currently driving close to a lane delimiter. This lane relative position can be used for providing information to the driver to support him in the task of safe centered driving. Such assisted centered driving becomes more important, because new vehicles often are less clearly laid out an thus the driver has difficulties in recognizing the relative position of the vehicle in the lane himself.
This lane relative position can also be used directly for other driver assistance systems such as lane keeping assistance systems or lane departure warning assistance systems or for autonomous driving.